Cancellation of RF second-order intermodulation distortion

ABSTRACT

The disclosed invention relates to a transceiver system configured to cancel RF second-order intermodulation distortion (IMD 2 ) within a differential reception path. In some embodiments, the transceiver system has one or more common-mode attenuation elements that attenuate common-mode interferer signals within the differential reception path. The common-mode attenuation elements detect a common-mode interferer from one or more nodes within a transceiver system front-end. One or more properties of the detected common-mode interferer are adjusted and then fed into the differential reception path, where the adjusted common-mode signal attenuates the common-mode interferers. In other embodiments, the differential reception path has a tunable amplifying stage. The tunable amplifying stage has first and second amplifier elements that are independently operated to intentionally introduce an operating parameter mismatch between the elements. The intentional mismatch may be tuned to account for different nonlinear responses of the amplifier elements to mitigate IMD 2  within the differential reception path.

BACKGROUND

Many modern wireless communication devices (e.g., cell phones, PDAs,etc.) utilize transceivers having both a transmitter section (i.e.,transmission chain) configured to transmit data and a receiver section(i.e., receiver chain) configured to receive data over radiofrequencies.

For example, FIG. 1 a illustrates a wireless communication transceiver100 comprising a transmitter section 102 and a receiver section 104. Inorder to reduce the hardware used by transceiver 100, a duplexer 106 maybe configured to couple both transmitter section 102 and receiversection 104 to a common antenna 108. To achieve high data rates,transceiver 100 may be configured to operate in full-duplex mode,wherein both transmitter section 102 and receiver section 104 useantenna 108 at the same time. During full-duplex mode operation,transmitter section 102 typically uses one carrier frequency whilereceiver section 104 uses another carrier frequency.

Despite using different frequencies, intermodulation distortion mayarise during operation of transceiver 100. Intermodulation distortionoccurs when a modulated blocker passes a component with a nonlinearcharacteristic, forming a spurious signal (e.g., an additional signal ata frequency that are not at harmonic frequencies of a received signal,but are instead at a sum and difference of the original signalfrequency) in a reception path that interferes with a receiveddifferential input signal.

Second-order intermodulation distortion is caused by multiplication oftwo interferer signals. FIG. 1 b illustrates a frequency graph 110showing an RF second-order intermodulation distortion (i.e., secondorder intermodulation distortion at RF frequencies) generated byinterferer signals. As illustrated in graph 110, the frequency domaincomprises a plurality of interferer signals at frequencies f1, f2, andf3. Although the frequencies of the interferer signals are not close toa received differential input signal frequency f_(R), the interferersignals may combine together to form spurious signals, 112 and 114,comprising products having a sum or difference of their frequencies(e.g., f1+f2, f3−f2). Spurious signals that land at an RF frequencyoccupied by received differential input signal frequency f_(R) causesecond-order intermodulation distortion that is detrimental to operationof the transceiver system. Once intermodulation distortion appearswithin the reception path, there is no way of distinguishing it from thedesired signal and transceiver sensitivity is degraded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a illustrates a block diagram of a transceiver system withsecond-order intermodulation distortion in the reception path.

FIG. 1 b is a graph showing the effect of second-order intermodulationdistortion within the frequency domain.

FIG. 1 c shows graphs illustrating the effect of common-mode interfererson a received differential input signal.

FIG. 2 illustrates a block diagram of an exemplary transceiver systemconfigured to attenuate RF second-order intermodulation distortionwithin a reception path.

FIG. 3 illustrates a block diagram of an exemplary transceiver systemcomprising a tunable amplifying stage having one or more amplifierelements configured to introduce operating parameter mismatches betweendifferential branches of a reception path.

FIG. 4 illustrates a block diagram of an exemplary transceiver systemcomprising one or more common-mode attenuation elements configured toattenuate common-mode interferer signals within a reception path.

FIGS. 5 a-5 b illustrate schematic diagrams of an exemplary tunableamplifying stage comprising one or more amplifier elements, as providedherein.

FIG. 6 illustrates a schematic diagram of an exemplary common-modeattenuation element.

FIG. 7 is a flow diagram of an exemplary method of reducing RFsecond-order intermodulation distortion by intentionally generatingoperating parameter mismatches between differential branches of areception path.

FIG. 8 illustrates a flow diagram of another exemplary method ofreducing RF second-order intermodulation distortion by attenuatingcommon-mode interferer signals within a reception path.

FIG. 9 is a flow diagram of an exemplary method for calibratingoperating parameter mismatches between differential branches of areception path.

FIG. 10 illustrates a flow diagram of an exemplary method forcalibrating attenuation of common-mode interferer signals within areception path.

FIG. 11 illustrates an example of a mobile communication device, such asa mobile handset, in accordance with the disclosure.

FIG. 12 illustrates an example of a wireless communication network inaccordance with the disclosure.

DETAILED DESCRIPTION

The claimed subject matter is now described with reference to thedrawings, wherein like reference numerals are used to refer to likeelements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the claimed subject matter. It may beevident, however, that the claimed subject matter may be practicedwithout these specific details.

It will be appreciated that “RF second-order intermodulation distortion”is second-order intermodulation distortion that is specifically locatedat an RF frequency (e.g., that is present in a receiver path beforedownconversion). This is in contrast to baseband (BB) second-orderintermodulation noise, which is a distortion that is present at low,baseband frequencies (i.e., which deteriorates RX performance afterdownconversion). The disclosed apparatus and techniques disclosed hereinrelate to mitigation of RF second-order intermodulation noise.

RF intermodulation distortion typically occurs when a transmitted signalleaks into a reception path due to limited isolation provided by aduplexer. However, even modern duplexers that offer good isolation do soat the expense of a common-mode interferer component being fed to thereception path. Filters may be used to remove unwanted interferers fromthe reception path. However, such filtering is expensive to implement inproducts. Furthermore, if the filtering is not highly selective,interferers with considerable levels may still appear within thereception path. For example, as shown in graph 110, the frequency domainmay be filtered, but still pass a frequency range Δf that includes adifferential input signal and close by spurious signals.

The inventors have appreciated that there are two major mechanisms thatcontribute to RF second-order intermodulation distortion in differentialtransceiver systems. The first mechanism is mismatches betweentransistor devices in nonlinear RF amplifiers. In particular, there areoperational mismatches between amplifier elements configured to amplifyeach of the two differential branches in a differential reception path.The operational mismatches lead to different nonlinear responses betweenthe two differential branches and thus to RF second-orderintermodulation distortion.

The second mechanism is the common-mode components of interferersignals. The common-mode components of interferer signals may causeproblems when the interferer signals are processed alongside of a wanteddifferential input signal. For example, FIG. 1 c illustrates theinfluence of a common-mode interferer signal on a total input signal fortwo differential branches in a reception path. A first differentialbranch 116 comprises an input signal having differential (DIFF)components, which are in phase with an interferer signal havingcommon-mode (CM) components (i.e., a common-mode interferer signal). Theresulting “total” signal has a first magnitude M₁ equal to the sum ofthe differential and common-mode components. A second differentialbranch 118 comprises an input signal having differential (DIFF)components that are out of phase with a common-mode interferer signal.The resulting “total” signal has a second magnitude M₂ that is differentthan magnitude M₁, causing different second-order intermodulationdistortion responses even when applied to a perfectly matcheddifferential nonlinear amplifier in the reception path.

Accordingly, a transceiver system configured to cancel RF second-orderintermodulation distortion is provided herein. The disclosed transceiversystem is configured to cancel RF second-order intermodulationdistortion arising from at least one of the two above identifiedmechanisms that contribute to RF second-order intermodulation distortionin differential transceiver systems.

In some embodiments, the transceiver system comprises a reception pathhaving a tunable amplifying stage comprising first and second amplifierelements configured to respectively amplify differential components of areceived differential input signal. The first and second amplifierelements are independently operated to intentionally introduce anoperating parameter mismatch (e.g., a gain coefficient mismatch) betweenthe first and second amplifier elements having a specific value. Theintentional operating parameter mismatch may be tuned to account fordifferent nonlinear responses of the two amplifier elements so as tomitigate RF second-order intermodulation distortion within the receptionpath.

In other embodiments, the transceiver system may additionally oralternatively comprise one or more common-mode attenuation elements. Thecommon-mode attenuation elements are configured to attenuate common-modeinterferer signals within the differential reception path. Inparticular, the common-mode attenuation elements are configured todetect a common-mode interferer signal from one or more nodes within afront end of the transceiver system. One or more properties of thedetected common-mode interferer signals are adjusted and then theadjusted common-mode signal is fed back into the reception path, wherethe adjusted common-mode signal attenuates the common-mode interferersignals without substantially deteriorating a received differentialinput signal.

FIG. 2 illustrates an exemplary block diagram of a front end of atransceiver system 200 configured to mitigate RF second-orderintermodulation distortion within a reception path.

Transceiver system 200 comprises a transmission path and a receptionpath. The transmission path is configured to provide a transmittedsignal TX to an antenna 202 by way of a duplexer 204. The reception pathis configured to receive an RF input signal from antenna 202. The RFinput signal is provided to duplexer 204, which outputs a differentialinput signal along first and second differential branches, 206 and 208respectively, of the reception path.

A nonlinear tunable amplifying stage 210 is configured to receive thedifferential input signal from duplexer 204. Tunable amplifying stage210 comprises a first amplifier element 210 a and a second amplifierelement 210 b. First and second amplifier elements, 210 a and 210 b, areconfigured to separately amplify components of the differential inputsignal before it is demodulated by a downstream mixer 216. For example,first amplifier element 210 a is configured to amplify components of thedifferential input signal on the first differential branch, while secondamplifier element 210 b is configured to amplify components of thedifferential input signal on the second differential branch.

A control unit 212 is configured to provide control signals S_(CTRL) toat least one of amplifier elements 210 a and 210 b. The control signalsS_(CTRL) independently control operating parameters of amplifierelements 210 a or 210 b. In some embodiments, control unit 212 isconfigured to provide a control signal to one of amplifier elements 210a and 210 b. In some alternative embodiments, control unit 212 isconfigured to provide a first control signal to first amplifier element210 a and a different, second control signal to second amplifier element210 b.

By independently controlling amplifier elements 210 a and 210 b, whichseparately amplify different components of the differential inputsignal, an intentional mismatch in operating parameters of amplifierelements 210 a and 210 b may be introduced. The intentional operatingparameter mismatch may be chosen to have a specific value (e.g., arelative gain coefficient mismatch factor) that accounts for mismatchesbetween transistor devices within amplifier elements 210 a and 210 b. Byaccounting for mismatches between transistor devices within amplifierelements 210 a and 210 b, the nonlinear response of two differentialbranches may be reduced, thereby reducing RF second-orderintermodulation noise. In some embodiments, the operating parametermismatch may comprise a mismatch in gain (i.e., gain coefficients) offirst and second amplifier elements 210 a and 210 b, for example.

Transceiver system 200 may alternatively or additionally comprise one ormore common-mode attenuation elements 214. The common-mode attenuationelements 214 are configured to detect common-mode interferer signal(s)CM_(INT) from one or more independent nodes in the front-end oftransceiver system 200 (e.g., the transmit path or input of amplifyingstage 206). One or more properties of the detected common-modeinterferer signal(s) are adjusted (e.g., magnitudes, phases, groupdelays, etc.) to form an adjusted common-mode signal CM_(INT)′ that isfed back into the reception path. Since the adjusted common-mode signalCM_(INT)′ is based upon the detected common-mode interferer signalCM_(INT) it may attenuate the common-mode interferer signal CM_(INT)without affecting the differential input signal received from antenna202.

In some embodiments, the adjusted common-mode signal CM_(INT)′ may befed back into the reception path at a downstream location. It will beappreciated that the term “downstream location” refers to a locationthat is downstream in relation to a detected interferer signal. Forexample, for an interferer signal that leaks from a transmission path toa reception path, any node within the reception path is downstream ofnodes within the transmission path since the interferer signal flowsform the transmission path to the reception path.

Control unit 212 may be further configured to provide control signalsS_(CTRL) to common-mode attenuation elements 214 to control adjustmentsto the one or more properties of the detected common-mode interferersignal CM_(INT). In some embodiments, one or more common-modeattenuation elements 214 are located within a feed-forward path. Thefeed-forward path may extend from a location upstream of tunableamplifying stage 210 to the output of tunable amplifying stage 210.

It will be appreciated that RF second-order intermodulation distortionwithin the reception path may be mitigated using one or both of thedisclosed apparatus (e.g., tunable amplifying stage 210 or common-modeattenuation elements 214) depending on which RF second-orderintermodulation generation mechanism dominates in a given transceiverdesign. For example, in some embodiments a transceiver system maycomprise a tunable amplifying stage 210 but not common-mode attenuationelements 214. In other embodiments, a transceiver system may compriseone or more common-mode attenuation elements 214 but not a tunableamplifying stage 210.

For successful application of the proposed RF second-orderintermodulation distortion reduction techniques, specific amounts/valuesof intentional mismatch and/or common-mode signal injection have to bedetermined. In some embodiments, a calibration element 216 may beconfigured to enable a calibration procedure that determines thespecific amounts/values of intentional mismatch and/or common-modesignal injection. For example, calibration element 216 may be configuredto provide test signals to one or more nodes in the front-end oftransceiver system 200. Calibration element 216 then measures one ormore parameters indicative of RF second-order intermodulation distortioncaused by the test signal within the reception path, and adjustssettings of the common-mode attenuation elements 214 and/or tunableamplifying stage 210 to successfully reduce RF second-orderintermodulation distortion.

In various embodiments, the calibration procedures may be done with acalibration element 216 comprising an external test source (i.e., as a“factory calibration”) or with a calibration element 216 comprising aninternal test source (i.e., as a “field calibration”). Since thecommon-mode signal levels are determined to a large extent by passiveexternal devices of the RF engine, using an external test source allowsfor the calibration task to be carried out based upon those devices.

For example, since RF second-order intermodulation distortion is largelyintroduced by the duplexer, the specifications of the duplexer may beused to properly determine how much the duplexer contributes to thegeneration of the unwanted common-mode signal, thereby effectivelybacking out the effect of the duplexer from the differential inputsignal. Furthermore, the use of an internal test source allows for thetransceiver system to perform calibration dynamically during operationof the transceiver system, thereby allowing the system to account forchanges that occur during operation. Exemplary calibration techniquesare described in more detail below in exemplary methods 900 and 1000.

It will be appreciated that by reducing second-order intermodulationdistortion that results from a transmitted signal leaking into thereception path, the disclosed apparatus and techniques allow forduplexers having a relatively low isolation to be used, thereby reducingthe cost of the transceiver system. In some embodiments, the disclosedsecond-order intermodulation cancellation apparatus and techniques cansufficiently reduce second-order intermodulation distortion so as toprovide a transceiver system that does not have a duplexer configuredbetween the reception path and a transmitter path.

FIG. 3 illustrates an exemplary block diagram of a transceiver front-end300 having a differential reception path comprising a tunable amplifyingstage 308, as disclosed herein. Tunable amplifying stage 308 isconfigured to implement intentional gain coefficient mismatching betweenamplifier elements operating in separate differential branches toaccount for amplifier device mismatches. The intentional gaincoefficient mismatching reduces RF second-order intermodulationdistortion within the differential reception path.

In particular, a duplexer 302 is connected to a differential receptionpath configured to conduct a differential input signal. When interferersignals, present in duplexer 302, are passed through a nonlinearamplifying stage 308 an RF second-order intermodulation distortionappears in the differential reception path.

The differential reception path has a first differential branch 304 anda second differential branch 306. First differential branch 304 isconnected to a first input node In_(p) of a first amplifier element 308a and second differential branch 306 is connected to a second input nodeIn_(n) of a second amplifier element 308 b. First and seconddifferential branches 304 and 306 are configured to respectivelytransmit a differential N-P complementary input signal from duplexer 302to first and second amplifier elements 308 a and 308 b.

First amplifier element 308 a is configured to receive first inputsignal components X_(P1) and X_(P2) at first input terminal In_(P).First amplifier element 308 a operates upon first input signalcomponents X_(P1) and X_(P2) to output a first order product, comprisinga first order gain coefficient g_(1P) multiplied by first input signalcomponents X_(P1) or X_(P2) (e.g., G_(1P)X_(P1) or G_(1P)X_(P2)), at afirst output terminal Out_(P). First output terminal Out_(P) alsooutputs a second order product comprising a second order gaincoefficient g_(2P) multiplied by a mixture of first input signalcomponents X_(P1) and X_(P2) (e.g., G_(2P)X_(P1)X_(P2)).

Second amplifier element 308 b is configured to receive second inputsignal components X_(N1) and X_(N2) at second input terminal In_(n).Second amplifier element 308 b operates upon second input signalcomponents X_(N1) and X_(N2) to output a first order product, comprisinga first order gain coefficient g_(1N) multiplied by second input signalcomponents X_(N1) or X_(N2) (e.g., G_(1N)X_(N1) or G_(1N)X_(N2)) at asecond output terminal Out_(n). Second output terminal Out_(n) alsooutputs a second order product comprising a second order gaincoefficient g_(2N) multiplied by a mixture of second input signalcomponents X_(N1) and N_(X2) (e.g., G_(2N)X_(N1)X_(N2)).

By expressing first and second input signal components, X_(P) and X_(N),in terms of their common-mode components X_(CM) and differentialcomponents X_(diff),X _(P) =X _(CM) +X _(diff)/2  (1)X _(N) =X _(CM) −X _(diff)/2,  (2)a differential output second-order intermodulation signal Y_(IMD2, DIFF)may be expressed as:Y _(IMD2,DIFF) =g _(2P) X _(P1) X _(P2) −g _(2N) X _(N1) X _(N2).  (3)wherein the single-sided second-order gain coefficients, g_(2P) andg_(2N), may be written as:g _(2P) =g ₂(1+Δg ₂)  (4a)g _(2N) =g ₂(1−Δg ₂)  (4b)where Δg2 is a relative mismatch factor of the second-order gaincoefficient, defined as Δg₂=(g_(2P)−g_(2N))/(g_(2P)+g_(2N)). Based uponthese definitions, the second-order differential distortion signalY_(IMD2,DIFF) may be written in terms of circuit parameters, as:Y _(IMD2,DIFF) =g ₂ [X _(CM1) X _(diff2) +X _(CM2) X _(diff1)+2Δg ₂(X_(CM1) X _(CM2)+(X _(diff1) +X _(diff2))/4)]  (5)wherein X_(CM1) is the common-mode signal at a first frequency andX_(CM2) is the common-mode signal at a second frequency. The resultingRF second-order differential distortion signal Y_(IMD2,DIFF) has threecomponents. The first two components are the cross products of thecommon-mode signals X_(CMx) and the differential signals X_(diffx) ofthe input interferer signals. The third term depends on mismatchesbetween second-order gain coefficients Δg₂ of the amplifying devices.

By intentionally mismatching gain coefficients of first and secondamplifier elements 308 a and 308 b the differences in the nonlinearresponses between first and second amplifier elements 308 a and 308 bmay be removed. Removing differences in the nonlinear responses causesthe relative mismatch factor of second-order gain coefficient Δg2 to goto zero, thereby reducing second-order differential distortion withinthe reception path by causing the third term of second-orderdifferential distortion signal Y_(IMD2,DIFF) to disappear.

One of ordinary skill in the art will appreciate that the gain of atransistor device is a function of the transistor width to channellength ratio, such that increasing the channel width increases the gainof the device. Therefore, in some embodiments, the intentional gaincoefficient mismatching of amplifier elements 308 a and 308 b may beperformed by adjusting the effective widths of transistor devices withinfirst or second amplifier elements 308 a and 308 b in an unequal manner.For example, the effective width of transistor devices may be changed inone of amplifier elements 308 a and 308 b without changing the effectivewidth of transistor devices in the other one of amplifier elements 308 aand 308 b. It will be appreciated that the term “effective width” asapplied herein refers to the cumulative width of transistor deviceswithin an amplifier element. For example, since amplifiers typicallycomprise a plurality of transistor devices, the effective widths oftransistor devices may be adjusted by adjusting the number of transistordevices that are turned on in an amplifier element.

In some embodiments, the existing circuitry used to change the effectivewidth of transistor devices may be reused for intentionally mismatchinggain coefficients of amplifier elements 308 a and 308 b. For example, incertain applications wherein device widths are modified to compensatefor process and temperature variations, existing circuitry (e.g.,switches, digital logic) may be reused to a large extent forintentionally mismatching of amplifier elements 308 a and 308 b.

FIG. 4 illustrates a block diagram of a front end of an exemplarytransceiver circuit 400 configured to attenuate common-mode interferersignals. Transceiver circuit 400 comprises one or more common-modeattenuation elements configured to detect the common-mode of interferersignals, to adjust one or more parameters of the detected common-modesignals (e.g., amplitude, phase, delay, etc.), and then to feed theadjusted common-mode signal back into the reception path to cancel thecommon-mode interferer signals. By attenuating the common-modeinterferer signals without adjusting the differential input signals,second order intermodulation noise is reduced without substantiallydeteriorating the differential input signals received by the antenna.

It will be appreciated that since the interferers may be separated fromone another by a large frequency range (e.g., hundreds of MHz),transceiver circuit 400 may be configured to independently detect andadjust different common-mode interferer signals. In some embodiments,transceiver circuit 400 may comprise a first common-mode attenuationelement 414 configured to attenuate common-mode interferers at a firstfrequency and a second common-mode attenuation element 422 configured toattenuate common-mode interferers at a second frequency.

For example, if transceiver circuit 400 is operated in full-duplex modea first interferer signal 406 is generated from the transmitted signalin a transmitter section 402 leaking through duplexer 410 into areception path of a receiver section 404. First interferer signal 406may be attenuated by first common-mode attenuation element 414 connectedbetween transmitter section 402 and receiver section 404. As illustratedin FIG. 4, first common-mode attenuation element 414 may comprise aconversion unit 416 configured to receive a single ended TX signal froma power amplifier 412. Conversion unit 416 converts the single endedsignal TX signal to a common-mode signal and detects the common-mode offirst interferer signal 406 therefrom. Conversion unit 416 is alsoconfigured to adjust properties of the detected common-mode signal. Theadjusted common-mode signal is then injected into the reception path ata location downstream of a low noise amplifier (LNA) 418. The adjustedcommon-mode signal attenuates RF second-order intermodulation distortionwithin receiver section 404 (i.e., makes X_(CM1)X_(diff2) approximatelyzero).

In various embodiments, conversion unit 416 may adjust propertiesincluding but not limited to the phase, magnitude, and/or signal delayof the detected common-mode of the first interferer signal. For example,in some embodiments, conversion unit 416 is configured to add a phaseoffset of 180° to the detected common-mode signal. The 180° phase offsetcauses the sign of the detected common-mode signal to change so thatwhen the adjusted common-mode signal is reinserted into the receptionpath, the common-mode signal component (X_(CM1)) is minimized (e.g., setto approximately zero). In some embodiments, a feedback receiver (FBR)input 420 may be used in power amplifier linearization systems as areference node.

Transceiver circuit 400 may additionally or alternatively have a secondcommon-mode attenuation element 422 comprising a feed-forward pathconfigured to attenuate a second interferer signal 408. The feed-forwardcommon-mode signal path extends from an input of low noise amplifier(LNA) 418 to an output of LNA 418. The feed-forward path comprises acommon-mode detection element 424 and a common-mode adjustment element426.

Second common-mode detection element 418 is configured to detect thecommon-mode of second interferer signal 408 in the reception path.Common-mode detection element 424 then outputs the detected common-modesignal to common-mode adjustment element 426. Common-mode adjustmentelement 426 is configured to make adjustments to properties of thedetected common-mode signal independent from the common-mode signaldetected in the transmitter section 402 (which may contain common-modecomponents at different frequencies). The adjusted properties mayinclude but are not limited to the phase and/or magnitude of thedetected common-mode signal of second interferer signal 408. Theadjusted common-mode signal is then output into the reception path,attenuating RF second-order intermodulation distortion within receiversection 404 (i.e., making X_(CM2)X_(diff1) approximately zero).

Accordingly, by utilizing two separate common-mode attenuation elements414 and 422, the common-mode of multiple interferer signals (e.g., 406and 408) may be effectively reduced. This reduces RF second-orderdifferential distortion within the reception path by causing the firstand second terms (X_(CM1)X_(diff2) and X_(CM2)X_(diff1)) of the secondorder differential distortion signal Y_(IMD2,DIFF) disappear.

FIG. 5 a illustrates a schematic diagram of a tunable differentialamplifying stage 500 comprising two amplifier elements, 502 and 504,configured to operate as transconductors (e.g., having atransconductance gm). The effective width of one or more of amplifierelements 502 and 504 may be dynamically adjusted by one or more controlsignals to induce transistor device gain coefficient mismatches betweenamplifier elements 502 and 504. As shown in FIG. 5 a, first amplifierelement 502 is configured to receive a first control signal S_(CTRLp)and second amplifier element 504 is configured to receive a secondcontrol signal S_(CTRLn), which is independent of the first controlsignal S_(CTRLp). Tunable differential amplifying stage 500 amplifiesreceived differential input voltages V_(inp) and V_(inn) based uponcontrol signals S_(CTRLp)S and S_(CTRLn) to generate differential outputcurrents I_(outp) and I_(outn).

FIG. 5 b illustrates a circuit diagram 506 of an exemplaryimplementation of amplifier element 504 shown in FIG. 5 a. Circuitdiagram 506 comprises a plurality of amplifying transistor devices 508and a plurality of switching transistor devices 510. Amplifyingtransistor devices 508 have gates connected to a node providing an inputvoltage V_(inn), and drains connected to a node providing an outputcurrent I_(outn). Switching transistor devices 510 have a drainconnected to a source of an associated amplifying transistor device, asource connected to ground, and a gate connected to a control wordS_(CTRLn). The control word S_(CTRLx) selectively activates switchingtransistor devices 510 to compensate for gain coefficient mismatchesbetween amplifier elements 502 and 504. For example, when a switchingtransistor device (e.g., T_(SW) _(—) ₁, T_(SW) _(—) ₂, etc.) is turnedon, its drain becomes connected to ground increasing the V_(GS) andaccordingly the current output from an associated amplifying transistor(since I_(d)=K·(W/L)·(V_(GS)−V_(th))²). When the switching transistor isturned off, V_(GS) of the amplifying transistor is decreased and thecurrent output from the amplifying transistor is reduced.

Therefore, if the control word S_(CTRLn) turns on transistor devicesT_(SW) _(—) ₁ and T_(SW) _(—) ₂, the amplifier element 504 will have aneffective width that results in a first gain coefficient and a firstoutput current value. However, if control word S_(CTRLn) only turns ontransistor device T_(SW) _(—) ₁, the amplifier element 504 will have asmaller effective width that results in a second gain coefficient and asecond output current value, which are respectively smaller than thefirst gain coefficient and the first output current value.

In some embodiments, the first and second control signals, S_(CTRL)p andS_(CTRLn), may comprise tuning codes having a control-voltage, bitstreaming, or control word, for example. In one embodiment, a controlsignal S_(CRTL) comprising a digital control word having a plurality ofk data bits is provided to a selection circuit 512. Based upon values ofthe plurality of k data bits in the received control word, the selectioncircuit 512 sends an activation voltage to selected switching transistordevice gates, causing the selected switching transistor devices to turnon and thereby increase the effective width of the amplifier element504. In some embodiments, the mean value of tuning codes provided toamplifier elements 502 and 504 may be determined by a transconductancealignment algorithm, wherein their difference is set in order to balancesecond-order transconductances.

FIG. 6 illustrates a schematic diagram of a transceiver circuit 600comprising a common-mode attenuation element. The common modeattenuation element 602 comprises a common mode detection element 604and an adjustment element 610.

Common-mode detection element 604 is configured to detect a common-modevoltage signal at the input of low-noise amplifier (LNA) 614 by usingtwo matched resistors R₁ and R₂. The detected common-mode voltage signalis sent to paths 606 and 608, respectively comprising filter capacitorsC₁ and C₂ which pass RF signals and that block DC signals, whichprovides the signals to adjustment element 610.

Adjustment element 610 comprises a biasing voltage V_(bias) that isadded to the detected common-mode voltage signal of paths 606 and 608.The biasing voltage V_(bias) activates the gates of single-endedamplifiers based around transistors T₁ and T₂. The gains of amplifyingtransistors T₁ and T₂ can be scaled to vary the output signal. Path 608further comprises a passive RC-filter, comprising resistor R₅ andcapacitor C₃, which introduces certain phase shift into the detectedcommon-mode voltage signal.

The output of transistors T₁ and T₂ is added to provide a current havinga certain phase and magnitude, which is copied by current mirror 612,comprising transistors T₃-T₅, to generate common-mode output signal thatis injected into the reception path. Current mirror 612 is configured togenerate the common-mode output signal as a function of the detectedcommon-mode voltage signal, so that the common mode output signalcompensates for the common-mode of an interferer signal in the receptionpath (e.g., taking into account the behavior of LNA 614).

FIG. 7 is a flow diagram of an exemplary method 700 of reducing RFsecond-order intermodulation distortion by intentionally generatingoperating parameter mismatches between differential branches of areception path.

It will be appreciated that while the methods disclosed herein (e.g.,methods 700, 800, 900, and 1000) are illustrated and described below asa series of acts or events, it will be appreciated that the illustratedordering of such acts or events are not to be interpreted in a limitingsense. For example, some acts may occur in different orders and/orconcurrently with other acts or events apart from those illustratedand/or described herein. In addition, not all illustrated acts may berequired to implement one or more aspects or embodiments of thedisclosure herein. Also, one or more of the acts depicted herein may becarried out in one or more separate acts and/or phases.

Furthermore, the disclosed methods may be implemented as a apparatus, orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof to control a computer to implement the disclosed subject matter(e.g., the circuits shown in FIGS. 2, 3, 4, etc., are non-limitingexamples of circuits that may be used to implement the disclosedmethods). The term “article of manufacture” as used herein is intendedto encompass a computer program accessible from any computer-readabledevice, carrier, or media. Of course, those skilled in the art willrecognize many modifications may be made to this configuration withoutdeparting from the scope or spirit of the claimed subject matter.

At 702 a differential reception path having a tunable amplifying stageis provided. The tunable amplifying stage comprises a first amplifierelement within a first differential branch and a second amplifierelement within a second differential branch. The differential receptionpath is configured to convey a differential input signal having an RFsecond-order intermodulation distortion.

At 704 the first and/or second amplifier elements are independentlyoperated to introduce an operating parameter mismatch between the firstand second amplifier elements. The operating parameter mismatch ischosen to have a specific value that mitigates the RF second-orderintermodulation distortion within the differential reception path. Insome embodiments, the operating parameter mismatch comprises a mismatchof gain coefficients of the amplifier elements. In such an embodiment,the effective widths of the first and/or second amplifier elements maybe dynamically adjusted. In some embodiments, a processor (e.g.,processor 1102 in FIG. 11) may execute instructions stored in a memory(e.g., memory 1104 in FIG. 11) to operate the first and/or secondamplifier elements to introduce the operating parameter mismatch.

FIG. 8 illustrates a flow diagram of another exemplary method 800 ofreducing second order intermodulation distortion by attenuatingcommon-mode interferer signals within a reception path. It will beappreciated that in some embodiments, a processor (e.g., processor 1102in FIG. 11) may execute instructions stored in a memory (e.g., memory1104 in FIG. 11) to operate the common-mode attenuation element asprovided in method 800.

At 802 a power supply is operated to provide power to a transceiverfront-end having a differential reception path comprising a firstamplifier element within a first differential branch and a secondamplifier element within a second differential branch configured toconvey a differential input signal having second order intermodulationdistortion.

At 804 a common-mode attenuation element is operated to detect acommon-mode of an interferer signal from one or more nodes in the frontend of a transceiver circuit. In some embodiments, the one or more nodesmay comprise a first node within a transmission path of the transceivercircuit and a second node within a reception path of the transceivercircuit.

At 806 the common-mode attenuation element is operated to adjust one ormore properties of the detected common-mode interferer signal. Adjustingthe detected common-mode signal may comprise adjusting the magnitudeand/or phase and/or introducing a signal delay into the detectedcommon-mode signal. In some embodiments, the detected common-mode signalis adjusted to switch the sign of its magnitude.

At 808 the common-mode attenuation element is operated to inject theadjusted common-mode signal into the differential reception path. Theinjected adjusted common-mode signal attenuates the common-modeinterferer signal detected at the one or more nodes, thereby decreasingsecond order intermodulation distortion within the reception path.

FIG. 9 is a flow diagram of an exemplary method 900 of calibratingoperating parameter mismatches between differential branches of areception path. The method 900 of calibration operates by locallyinjecting common-mode test tones and detecting resulting differentialoutput signals. It will be appreciated that in some embodiments, aprocessor (e.g., processor 1102 in FIG. 11) may execute instructionsstored in a memory (e.g., memory 1104 in FIG. 11) to operate the controlunit and/or calibration element as provided in method 900.

At 902 a power supply is operated to provide power to a differentialtransceiver device having a tunable amplifying stage comprising firstand second amplifier elements within a differential reception path. Inparticular, the provided power turns on the differential transceiverdevice, which has a tunable nonlinear amplifying stage having a firstamplifier element within a first differential branch and a secondamplifier element within a second differential branch.

At 904 a control unit is operated to measure a differential outputstatic DC offset value in the differential reception path. Thedifferential output static DC offset value is a DC offset measuredbetween differential branches of a differential reception path.

At 906 a calibration element is operated to apply an interferer testsignal to the reception path. In some embodiments, the interferer testsignal comprises an amplitude modulated wave (e.g., having a squarewaveform at some intermediate frequency). The interferer test signal maybe injected in front of the nonlinear amplifying stage.

At 908 the control unit is operated to measure a differential outputtotal DC offset value in the differential reception path. Thedifferential output total DC offset value comprises contributions fromboth the differential output static DC offset and the interferer testsignal.

At 910 the control unit is operated to calculate the difference betweenthe measured differential output static DC offset value and the measureddifferential output total DC offset value. The difference between thestatic and total DC offset values is indicative of device mismatchesbetween the amplifier elements.

The control unit is operated to compare the calculated difference to apredetermined threshold value at 912. If the calculated difference isless than the predetermined threshold value, method 900 ends. However,if the calculated difference is greater than the predetermined thresholdvalue then the control unit adjusts settings (e.g., gain) of one or moretransceiver amplifier elements to change the operating parametermismatch at 914.

FIG. 10 illustrates a flow diagram of another exemplary method 1000 ofcalibrating attenuation of common-mode interferer signals within areception path. The method 1000 of calibration may require the injectionof test signals at an antenna port and at a transmission path. It willbe appreciated that although method 1000 describes calibration of firstand second common-mode attenuation elements, the method is not limitedto calibration of two common-mode attenuation elements. Rather, one ormore steps of the disclosed method 1000 may be utilized to calibrate anynumber of common-mode attenuation elements. Furthermore, it will beappreciated that in some embodiments, a processor (e.g., processor 1102in FIG. 11) may execute instructions stored in a memory (e.g., memory1104 in FIG. 11) to operate the common-mode attenuation elements and/orcalibration element as provided in method 1000.

At 1002 a power supply is operated to provide power to a differentialtransceiver device having a nonlinear amplifying stage within adifferential reception path. The provided power turns on a differentialtransceiver device. In some embodiments, the amplifying stage maycomprise a low noise amplifier (LNA).

At 1004 a calibration element is operated to apply a first interferertest signal to a transmitter path of the transceiver device. The firstinterferer test signal leaks into the differential reception path whereit has some common-mode components and some differential-modecomponents.

At 1006 a first common-mode attenuation element is operated to measure afirst common-mode interferer signal level within the reception path. Forexample, the first common-mode interferer signal level can be measuredat the output of the LNA.

At 1008 the first common-mode attenuation element is operated to detecta first reference signal at a first node within the transmitter path.

At 1010 the first common-mode attenuation element is operated to comparethe measured first common-mode interferer signal level to a firstpredetermined threshold value (TH_(pre) _(—) ₁). Comparison of themeasured first common-mode interferer signal to the first predeterminedthreshold value allows for changes in the common-mode attenuationelement to be made to so that the reference signal is as similar aspossible to the common mode level, but with opposite sign (so that thesum of both signals is minimized).

For example, if the measured first common-mode signal level is greaterthan the first predetermined threshold value then settings of the firstcommon-mode attenuation element are adjusted, to adjust one or moreproperties (e.g., phase, magnitude, and/or signal delay) of the firstreference signal at 1012. If the measured first common-mode signal levelis less than the first predetermined threshold value then thecalibration element is operated to disable the first interferer testsignal at 1014.

At 1016 the calibration element is operated to provide a secondinterferer test signal is applied to a reception path of the transceiverdevice. The second interferer test signal may be applied to an antennaport of the transceiver, for example.

At 1018 a second common-mode attenuation element is operated to measurea second common-mode interferer signal level within the reception path.The second common-mode interferer signal level can be measured at theoutput of the LNA.

At 1020 a second common-mode attenuation element is operated to detect asecond reference signal at one or more nodes within the reception path.

At 1022 the second common-mode attenuation element is operated tocompare the measured second common-mode signal level to a secondpredetermined threshold value (TH_(pre) _(—) ₂). If the measured secondcommon-mode signal level is less than the second predetermined thresholdvalue method 1000 ends. However, if the measured second common-modesignal level is greater than the second predetermined threshold valuethen settings of the second common-mode attenuation element areadjusted, to adjust one or more properties of the second referencesignal at 1024. In various embodiments, the properties may comprise thephase, magnitude and/or signal delay of the detected common-mode of thesecond interferer signal.

FIG. 11 and the following discussion provide a brief, generaldescription of a suitable mobile communication device 1100 to implementembodiments of one or more of the provisions set forth herein. Thismobile communication device 1100 is merely one possible device on whichsecond order intermodulation noise attenuation techniques as set forthabove may be implemented, and it will be appreciated that the noiseattenuation techniques may also be used with other devices (e.g.,individual digital chip sets, mixed-signal chip sets, and/or analog chipsets). Therefore, the mobile communication device 1100 of FIG. 11 isonly one example of a suitable operating environment and is not intendedto suggest any limitation as to the scope of use or functionality of theoperating environment. Example mobile communication devices include, butare not limited to, mobile devices (such as mobile phones, PersonalDigital Assistants (PDAs), media players, and the like), tablets,personal computers, server computers, hand-held or laptop devices,multiprocessor systems, consumer electronics, mini computers, mainframecomputers, distributed computing environments that include any of theabove systems or devices, and the like.

FIG. 11 illustrates an example of a mobile communication device 1100,such as a mobile phone handset for example, configured to implement oneor more embodiments provided herein. In one configuration, mobilecommunication device 1100 includes at least one processing unit 1102 andmemory 1104. Depending on the exact configuration and type of mobilecommunication device, memory 1104 may be volatile (such as RAM, forexample), non-volatile (such as ROM, flash memory, etc., for example) orsome combination of the two. Memory 1104 may be removable and/ornon-removable, and may also include, but is not limited to, magneticstorage, optical storage, and the like. In some embodiments, computerreadable instructions in the form of software or firmware 1106 toimplement one or more embodiments provided herein may be stored inmemory 1104. Memory 1104 may also store other computer readableinstructions to implement an operating system, an application program,and the like. Computer readable instructions may be loaded in memory1104 for execution by processing unit 1102, for example. Otherperipherals, such as a power supply 1108 (e.g., battery) and a camera1110 may also be present.

Processing unit 1102 and memory 1104 work in coordinated fashion alongwith a transceiver 1112 to wirelessly communicate with other devices byway of a wireless communication signal. To facilitate this wirelesscommunication, a wireless antenna 1120 is coupled to transceiver 1112.During wireless communication, transceiver 1112 may use frequencymodulation, amplitude modulation, phase modulation, and/or combinationsthereof to communicate signals to another wireless device, such as abase station for example. The previously described high resolution phasealignment techniques are often implemented in processing unit 1102and/or transceiver 1112 (possibly in conjunction with memory 1104 andsoftware/firmware 1106) to facilitate accurate data communication.However, the high resolution phase alignment techniques could also beused in other parts of mobile communication device.

To reduce second-order intermodulation noise within transceiver 1112,the mobile communication device 1100 also may include a tunableamplifying stage 1114 and/or one or more common-mode attenuationelements 1116 as previously described. The tunable amplifying stage 1114and/or one or more common-mode attenuation elements 1116 are configuredto cancel RF second-order intermodulation distortion arising from themechanisms herein identified that contribute to RF second-orderintermodulation distortion in differential transceiver systems. Acontrol unit 1118 is configured to send control signals to tunableamplifying stage 1114 and/or common-mode attenuation elements 1116. Insome embodiments, processing unit 1102 comprise control unit 1118.

To improve a user's interaction with the mobile communication device1100, the mobile communication device 1100 may also include a number ofinterfaces that allow the mobile communication device 1100 to exchangeinformation with the external environment. These interfaces may includeone or more user interface(s) 1122, and one or more device interface(s)1124, among others.

If present, user interface 1122 may include any number of user inputs1126 that allow a user to input information into the mobilecommunication device 1100, and may also include any number of useroutputs 1128 that allow a user to receive information from the mobilecommunication device 1100. In some mobile phone embodiments, the userinputs 1126 may include an audio input 1130 (e.g., a microphone) and/ora tactile input 1132 (e.g., push buttons and/or a keyboard). In somemobile phone embodiments, the user outputs 1128 may include an audiooutput 1134 (e.g., a speaker), a visual output 1136 (e.g., an LCD or LEDscreen), and/or tactile output 1138 (e.g., a vibrating buzzer), amongothers.

Device interface 1124 allows a device such as camera 1110 to communicatewith other electronic devices. Device interface 1124 may include, but isnot limited to, a modem, a Network Interface Card (NIC), an integratednetwork interface, a radio frequency transmitter/receiver, an infraredport, a USB connection, or other interfaces for connecting mobilecommunication device 1100 to other mobile communication devices. Deviceconnection(s) 1124 may include a wired connection or a wirelessconnection. Device connection(s) 1124 may transmit and/or receivecommunication media.

Mobile device 1000 may further comprise a self calibration signalgenerator 1140 configured to provide calibration signals to transceiver1112. As described above, in relation to methods 900 and 1000, thecalibration signals provided by self calibration signal generator 1140may be used to tune operation of tunable amplifying stage 1114 and/orcommon-mode attenuation elements 1116 to enable efficient reduction ofsecond-order intermodulation distortion.

FIG. 12 illustrates one embodiment of a wireless network 1200 over whicha mobile communication device (e.g., mobile communication device 1100 inFIG. 11) in accordance with this disclosure may communicate. Thewireless network 1200 is divided into a number of cells (e.g., 1202 a,1202 b, . . . , 1202 d), wherein each cell has one or more base stations(e.g., 1204 a, 1204 b, . . . , 1204 d, respectively). Each base stationmay be coupled to a carrier's network 1206 (e.g., a packet switchednetwork, or a circuit switched network such as the public switchedtelephone network (PSTN)) via one or more wirelines 1208.

A mobile device 1210 (e.g., mobile communication device 1100) or othermobile device, having a transceiver configured to implement anintentional gain coefficient mismatch and/or attenuation of common-modeinterferer signals to reduce second-order intermodulation noise, mayestablish communication with the base station within that cell via oneor more of frequency channels used for communication in that cell. Thecommunication between a mobile handset or other mobile device 1210 and acorresponding base station often proceeds in accordance with anestablished standard communication protocol, such as LTE, GSM, CDMA orothers. When a base station establishes communication with a mobilehandset or other mobile device, the base station may establishcommunication with another external device via the carrier's network1206, which may then route communication though the phone network.

Those skilled in the art will realize that mobile communication devicessuch as mobile phones may in many instances upload and download computerreadable instructions from a network through the base stations. Forexample, a mobile handset or other mobile device 1210 accessible vianetwork 1206 may store computer readable instructions to implement oneor more embodiments provided herein. The mobile handset or other mobiledevice 1210 may access a network and download a part or all of thecomputer readable instructions for execution.

The term “computer readable media” as used herein includes computerstorage media. Computer storage media includes volatile and nonvolatile,removable and non-removable media implemented in any method ortechnology for storage of information such as computer readableinstructions or other data. Memory (e.g., 1104 in FIG. 11) is an exampleof computer storage media. Computer storage media includes, but is notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, Digital Versatile Disks (DVDs) or other optical storage,magnetic cassettes, magnetic tape, magnetic disk storage or othermagnetic storage devices, or any other medium which may be used to storethe desired information. The term “computer readable media” may alsoinclude communication media. Communication media typically embodiescomputer readable instructions or other data in a “modulated datasignal” such as a carrier wave or other transport component and includesany information delivery media. The term “modulated data signal” mayinclude a signal that has one or more of its characteristics set orchanged in such a manner as to encode information in the signal.

Although the disclosure has been shown and described with respect to oneor more implementations, equivalent alterations and modifications willoccur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Further,it will be appreciated that identifiers such as “first” and “second” donot imply any type of ordering or placement with respect to otherelements; but rather “first” and “second” and other similar identifiersare just generic identifiers. In addition, it will be appreciated thatthe term “coupled” includes direct and indirect coupling. The disclosureincludes all such modifications and alterations and is limited only bythe scope of the following claims. In particular regard to the variousfunctions performed by the above described components (e.g., elementsand/or resources), the terms used to describe such components areintended to correspond, unless otherwise indicated, to any componentwhich performs the specified function of the described component (e.g.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary implementations of the disclosure. Inaddition, while a particular feature of the disclosure may have beendisclosed with respect to only one of several implementations, suchfeature may be combined with one or more other features of the otherimplementations as may be desired and advantageous for any given orparticular application. In addition, the articles “a” and “an” as usedin this application and the appended claims are to be construed to mean“one or more”.

Furthermore, to the extent that the terms “includes”, “having”, “has”,“with”, or variants thereof are used in either the detailed descriptionor the claims, such terms are intended to be inclusive in a mannersimilar to the term “comprising.”

What is claimed is:
 1. A transceiver system, comprising: a differential reception path having a first differential branch and a second differential branch configured to conduct a differential input signal having RF second-order intermodulation distortion; a tunable amplifying stage, located within the differential reception path, comprising a first amplifier element configured to operate upon the first differential branch and a second amplifier element configured to operate upon the second differential branch; and a control unit configured to control operating parameters of the first or second amplifier elements to introduce an operating parameter mismatch between the first and second amplifier elements that has a specific value that mitigates the RF second-order intermodulation distortion within the differential reception path.
 2. The transceiver system of claim 1, further comprising: a duplexer connected between the antenna and the tunable amplifying stage and configured to couple the reception path and a transmission path to an antenna.
 3. The transceiver system of claim 1, wherein the control unit is configured to independently control operating parameters of the first and second amplifier elements.
 4. The transceiver system of claim 1, further comprising: a calibration element configured to enable a calibration of the tunable amplifying stage to be performed to determine the specific value of the operating parameter mismatch of the tunable amplifying stage.
 5. The transceiver system of claim 1, wherein the control unit is configured to dynamically adjust the specific value of the operating parameter mismatch during operation of the transceiver system.
 6. The transceiver system of claim 1, wherein the operating parameter mismatch comprises a mismatch in gain coefficients of the first amplifier element and the second amplifier element.
 7. The transceiver system of claim 6, wherein the effective width of transistor devices within the first amplifier element are modified relative to the effective width of transistor devices within second amplifier element to achieve the mismatch in gain coefficients.
 8. The transceiver system of claim 1, wherein the control unit is further configured to generate a first control signal that is provided to the first amplifier element, wherein the first control signal controls the operating parameters of the first amplifier element in a manner that introduces the operating parameter mismatch between the first and second amplifier elements.
 9. The transceiver system of claim 8, wherein the control signal comprises a digital control word having a plurality of data bits.
 10. The transceiver system of claim 9, wherein the amplifier elements comprise: a plurality of switching transistor devices that are selectively activated based on the digital control word; and a plurality of amplifying transistor devices connected to the plurality of switching transistors, wherein respective amplifying transistors are configured to amplify a differential component of the differential input signal if an associated switching transistor is activated.
 11. The transceiver system of claim 1, further comprising: one or more common-mode attenuation elements, respectively configured to detect a common-mode interferer signal at one or more nodes within a front end of the transceiver system, to adjust one or more properties of the detected common-mode interferer signal, and to inject the adjusted common-mode interferer signal into the differential reception path; wherein the adjusted common-mode signal attenuates the common-mode interferer signal within the differential reception path.
 12. The transceiver system of claim 11, wherein the one or more common-mode attenuation elements comprise: a first common-mode attenuation element configured to detect and adjust a first common-mode interferer signal and a second common-mode attenuation element configured to independently detect and adjust a second common-mode interferer signal.
 13. A mobile handset, comprising: a processor; a memory; a transceiver configured to send and receive a wireless communication signal; a tunable amplifying stage, located within a differential reception path of the transceiver and comprising a first amplifier element configured to amplify signals within a first differential branch and a second amplifier element configured to amplify signals within a second differential branch; and a control unit configured to mitigate RF second-order intermodulation distortion within the differential reception path by independently operating the first and second amplifier elements to introduce a gain coefficient mismatch between the first and second amplifier elements.
 14. The mobile handset of claim 13, further comprising: one or more common-mode attenuation elements, respectively configured to detect a common-mode interferer signal at one or more nodes within a front end of the transceiver system, to adjust one or more properties of the detected common-mode interferer signal, and to inject the adjusted common-mode interferer signal into the differential reception path; wherein the adjusted common-mode signal attenuates the common-mode interferer signal within the differential reception path without deteriorating the differential input signal.
 15. The mobile handset of claim 13, wherein the gain coefficient mismatch comprises a mismatch in gain coefficients of the first amplifier element and the second amplifier element.
 16. The mobile handset of claim 15, wherein the mismatch in gain coefficients is achieved by modifying the effective width of transistor devices within the first amplifier element relative to the effective width of transistor devices within second amplifier element.
 17. A method for reducing second-order intermodulation distortion within a differential reception path of a transceiver system, comprising: operating a power supply to provide power to a differential reception path configured to convey a differential input signal having second order intermodulation noise, wherein the differential reception path comprises a tunable amplifying stage having a first amplifier element within a first differential branch and a second amplifier element within a second differential branch; and independently operating the first and second amplifier elements to introduce an operating parameter mismatch between the first and second amplifier elements that mitigates the RF second-order intermodulation distortion within the differential reception path.
 18. The method of claim 17, further comprising: operating a common-mode attenuation element to detect a common-mode interferer signal from one or more nodes within a front end of the transceiver system, operating the common-mode attenuation element to adjust one or more properties of the detected common-mode interferer signal to generate an adjusted common-mode signal; and operating the common-mode attenuation element to inject the adjusted common-mode signal into the differential reception path, wherein the adjusted common-mode signal attenuates the common-mode interferer signal within the reception path.
 19. The method of claim 17, wherein the operating parameter mismatch comprises a mismatch in the gain coefficients of the first amplifier element and the second amplifier element.
 20. The method of claim 17, further comprising performing a calibration of the operating parameter mismatch, wherein performing the calibration comprises: measuring a differential output static DC offset between differential branches of the reception path; operating a calibration element to apply an interferer test signal to the reception path; measuring differential output total DC offset value between differential branches of the reception path, wherein the differential output total DC offset value comprises contributions from the differential output static DC offset and the interferer test signal; and calculating a difference between the measured differential output total DC offset value and the measured differential output static DC offset value; and operating the calibration element to tune settings of the first and second amplifier elements if the calculated difference is above a predetermined threshold value. 